I claim the ornamental design for a sport jersey window flag, as shown and described.

Description

FIG. 1 is a front view of the sport jersey window flag;

FIG. 2 is a left side view of the sport jersey window flag;

FIG. 3 is a top/bottom view of the sport jersey window flag;

FIG. 4 is a back view of the sport jersey window flag; and,

FIG. 5 is a right side view of the sport jersey window flag.

The evenly spaced pattern of broken lines in the drawings represent a pattern of stitching. The long and short broken lines showing environment in the drawings are for illustrative purposes only and form no part of the claimed design.

The crisscross pattern of lines in the drawings represent material and is understood to be distributed uniformly over the surface of the flag.